Multiple Choice
Which of the following best describes the initial concentration (m) of sodium thiocyanate in a reaction mixture if 0.10 mol of NaSCN is dissolved in 1.0 L of solution?
1. Chemical Measurements
Chemical Concentrations
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Which of the following wavelengths (in nm) is most appropriate for measuring the absorbance of a yellow dye using UV-Vis spectrophotometry?
A
600 nm
B
300 nm
C
420 nm
D
700 nm
Verified step by step guidance1
Step 1: Understand the concept of complementary colors in UV-Vis spectrophotometry. A substance absorbs light at wavelengths corresponding to its complementary color. For a yellow dye, the complementary color is violet, which corresponds to wavelengths around 420 nm.
Step 2: Recall that UV-Vis spectrophotometry measures absorbance based on the interaction of light with the sample. The wavelength chosen should correspond to the maximum absorbance of the dye, which is typically near its complementary color.
Step 3: Analyze the given options: 600 nm (orange-red region), 300 nm (UV region), 420 nm (violet region), and 700 nm (red region). Among these, 420 nm is closest to the complementary color of yellow.
Step 4: Consider the practical application: Using 420 nm ensures the most accurate measurement of absorbance for the yellow dye because it corresponds to the wavelength where the dye absorbs light most strongly.
Step 5: Conclude that 420 nm is the most appropriate wavelength for measuring the absorbance of the yellow dye using UV-Vis spectrophotometry, as it aligns with the principles of complementary colors and maximum absorbance.
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